PCI caching question related to mvme5500
dufault at hda.com
Tue Nov 1 18:38:52 UTC 2005
On Nov 1, 2005, at 1:20 PM, gregory.menke at gsfc.nasa.gov wrote:
> This is essentially PIO mode, the slowest possible way of getting data
> off the PCI bus. If you're lucky it may burst but you can't confirm
> that without a bus analyzer. This is very likely why you're having
> performance issues. Its cutting your bus throughput by about a factor
> of 6. You should consider using DMA to get your data off the board.
ARG! I'm NOT having performance issues! I know it's bursting because
of the difference between with and without cacheing turned on. I'm
reading 32 bytes, what is that, one cache line? The board doc says:
"Burst read of PMC341 memory buffer will allow a 40Mbyte per second
data read rate".
But if I don't cache it I do have problems.
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